For diseases such as athlete's foot and candidiasis to be caused by fungi, medicaments such as bifonazole, butenafine, and terbinafine have been developed and prescribed as skin medicines for external use.
Of those, there may be exemplified, as a particularly promising medicament, a compound represented by a general formula (1) having an effect of shortening a therapeutic period for diseases derived from fungi, which has been reported in recent years as a novel imidazole compound having an antifungal activity, especially, luliconazole, which is an optically active substance (see JP 3278738 B). Further, such compound is also useful for onychomycosis, and a formulation for onychomycosis has also already been known (for example, see WO 03/105841). That is, the compound represented by the general formula (1) may be said as a useful active ingredient that may be widely used for mycoses (having an antifungal action).

It is generally known that an antifungal agent is used for a therapy for tinea (tinea pedis, tinea corporis, or tinea cruris), candidiasis (intertrigo or erosio interdigitalis blastomycetica), chromophytosis, or seborrheic dermatitis, for example. However, a formulation used for seborrheic dermatitis is applied to a scalp site around the hair, and thus is used in a larger amount compared with that used for mycoses of the body and mycoses of the hands and feet. Therefore, it is restricted to use a solvent such as methyl ethyl ketone from the viewpoints of possibility of causing an irritation, flammability, and the like. Accordingly, there has been a demand for a formulation that is free of any adverse effect such as an irritation and may be easily administered. In addition, in order to ensure an effect of an antifungal action, it is preferred that a formulation sufficiently dissolves a drug and be in a form of a single-phase solution. Because the compound represented by the general formula (1) has restricted water solubility, one problem is how to prepare a formulation in a form of a single-phase solution without impairing the solubility of the compound.
Meanwhile, various studies are being conducted in order to improve the stability of a bulk drug of an antifungal agent. In particular, in a compound having an asymmetric carbon in the molecule, the maintenance of a steric structure becomes a critical issue in addition to the solubility. This is because the steric structure may be easily changed in a dissolution state. Any of the addition of sugars (see JP 2000-169372 A) and the adjustment of a pH (see JP 06-065076 A) has been conducted as one measure for the above, for example. In addition, it is known that an imidazole derivative is easily dissolved by polyethylene glycol, to thereby provide satisfactory stability (see JP05-070351A). However, there is no definite law for maintenance property of such steric structure. Thus, it may be said that the case where the steric structure may be maintained is rare in itself. Further, such combination is incidentally found out under the present situation. In a formulation containing the compound represented by the general formula (1), there has been no finding about whether or not the maintenance of the steric structure of the compound becomes a problem, and further, it is not known how to achieve such maintenance of the steric structure. Under such backgrounds, in pharmaceutical administration and regulations, there is a demand for means for ensuring the stability suited for the compound represented by the general formula (1).
In addition, an alcohol typified by ethanol and water are widely used medium ingredients in formulation. It is known that those ingredients may cause hydrolysis or the like to affect the stability of an active ingredient. However, there has been no finding that the ingredients have a preferred contribution to the stability in a specified mixing ratio. Further, an anionic surfactant such as sodium dodecyl sulfate has been known to have a surfactant action and an action of promoting medicament permeability, but is not in any way known for its contribution to the stability.